Process for inhibition of mold



c. HOFFMAN Er AL, 2,154,449

PROCESS FOR INHIBITION OF MOLD April 18, 1939.

Filed June 15, 1938 AT VARIOUS H VALUES pH RANGE sa asaa assa s N (\l N (\l N QIVNOldOHd WQIDTIVQ :IO HDVINQDHQd Char/e5 Hoffman INVENTORS 061M021 Da/b ThOmcZJR \fichweiger y WA TORNEY Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE 2.154.449 Paocsss FOR mnrarrron or MOLD York Application June 15, 1938, Serial No. 213,908

.16 Claims.

This invention relates to materials susceptible to mold growth and more particularly to the inhibition or prevention of mold growth in materials susceptible thereto. This application is a continuation in part of our copending applications, S. N. #87356, filed June 26, 1936 and S. N. #113,552, filed December 1, 1936.

As is well known, foodstuffs such as bread, pastries, various cereal products, milk products such as butter and cheese, meats, wines, and in fact a multitude of products of animal or vegetable origin are susceptible in varying degrees to the growth of mold therein or thereupon which renders such materials unfit for human consumption.

Mold formation is caused by a species of microorganism which feeds upon a wide variety of different materials occurring in a natural or manufactured condition. The micro-organisms grow and propagate rapidly under favorable conditions'of humidity and temperature and, under unfavorable conditions such as insumcient moisture, they form highly resistant spores which readily become dispersed and scattered and immediately start a mold growth when humidity and other conditions are favorable.

Bread, for example, being moist and porous makes an excellent medium for the'growth of mold. Almost all of the common molds, Aspergillus nz'ger, Penicillium glaucus, Penicillium ea:- pansum, Rhizopus niaricans, Trichothecium roseum, various species of Mucor, etc., under the favorable conditions existing in undried bread grow rapidly on the surface of the loaf and between the slices if the bread be sliced. The wrapping of the bread and slicing it before wrapping have made the problem of molds more serious since the moisture-proof wrapper retains.

and holds the moistness of the loaf. As these molds render the bread unfit and possibly dangerous-for the'consumer, the molding of the bread even after being wrapped and sold is a constant source of expense and annoyance. Similar difliculties also occur in other goods such as cereal products, sweet butter, icings and othe products of animal or vegetable origin.

Owing to the wide diffusion of the mold spores it is substantially impossible to prevent their access to food products stored or processed under commercial conditions. As a result, mold formation rapidly sets in after such food products have been exposed to the'air either during processing or storage and when subjected to moisture and temperature conditions suitable for the growth of the mold.

7 carbon acids.

Various methods have been proposed to overcome mold growth, such for example as packaging foodstuffs so as to maintain an atmosphere of inert gases surrounding the foodstuffs; preparing the foodstuff, such as bread, in an atmosphere purified of mold spores; treating the foodstuff with germicides, or the like. All such prior proposals have been characterized, however, by great expense or by adverse effect upon the flavor, odor, edibility or food value of the treated product and as a consequence have not been commercially feasible. The problem of mold prevention in a manner practically operable, has, therefore, persisted without practical solution up to the present invention.

It is an object of this invention to obviate the disadvantages of the 'prior art and to provide a new and improved method for inhibiting the growth of mold in materials susceptible thereto.

It is a further object of this inention to provide a method of preventing mold in foodstuffs without adverse effect upon the treated product.

Other objects and advantages of this invention will be apparent from the following specification.

According to the present invention the growth 'of mold in materials susceptible thereto is inhibited by the treatment of such materials with, or by the incorporation therein or addition thereto of, a relatively small quantity of one or more saturated branched or straight chain monocaboxylic aliphatic acids of from 3 to 12 carbon atoms or salts of such acids. Thus, inhibition of mold growth may be accomplished in materials in which there may be incorporated one or more acids such as propionic and the branched and straight chain butyrics, valerics, caproics, heptoics, caprylics, nonylics, caprics, undecylics and lauric. It is also meant to include the salts of the various metals, especially the alkali and alkaline earth metals, as well as the ammonium, substitued ammonium and like salts of such 3 to 12 In the case of any of these salts it will be understood that they may be utilized as such or in the form of substances which will in the presence of moisture be converted at least in part to the salt, such, for example, as in the case of amides which, in the presence of water, will yield the ammoniumsalt; or in the case of adding the acid together with, subsequent to, or followed by an alkali or alkaline compound, the alkaline material being present in sumcient amount to neutralizethe acid.

The list of substances, other than the acids previously described, coming within the bounds of this invention could be extended greatly, but

by citing the following s c materlals which are useful as mold inhibitors according to this invention, the nature of the broader classifications will be made adequately clear. According to this invention, then, there may be utilized small quantities of such substances, or mixtures and equivalents thereof, as: sodium, calcium, potassium, magnesium, mercury, zinc, ammonium and like propoionates, butyrates, isobutyrates, valerates, caprylates, laurates, and the like. In the case of foodstuffs, although effective in inhibiting mold, the use of toxic or poisonous salts of the acids hereinbefore described, such as the zinc, mercury, barium and strontium salts, is, of course, avoided.

According to a further feature of this invention, improvement in the taste and quality of foodstuffs, mold inhibited as hereinbefore described, may be obtained, particularly in baked goods, by incorporation in .the foodstuff of a small quantity of an alkaline compound such as sodium or ammonium carbonate, bicarbonate, carbamate, urea or the like, or mixtures of such materials. Thus, in using a propionate salt, as an example, such as calciumpropionate, a quantity of the alkaline compound, such' as ammonium carbonate, or bicarbonate, equal to the quantity of inhibitor serves to improve greatly the quality of bread generally, as well as to improve the taste specifically. The quantities of alkaline material, such as ammonium carbonate or bicarbonate, used may be varied over a considerable range, such as from, say, 1 6 to of the quantity of inhibitor, altho a quantity approximately midway between these extremes is generally preferable, being based, as stated hereinbefore, upon the quantity of the inhibitor used.

The quantity of inhibitor, i. e. an acid or a salt of an acid, such as previously described,'or mixtures of such inhibitors, required to produce the optimum mold-inhibiting effect, is varied by, among other things, the specific pH value of the material treated. Generally speaking, however, an amount of salt equal to from about 0.01% to 2.3%, based upon the water content by weight of the material being treated, is preferred and suflicient to protect materials of pH 3 to '7 against mold formation. Smaller proportions may be utilized if lower pH values exist, and greater proportions if higher pH values, without departing from this invention. The variation of required concentration of inhibitor with variation of pH value is shown in the accompanying drawing, utilizing calcium propionate as an example, wherein the abscissa give the pH range and the ordinates the percentage of inhibitor (based on water content of the medium being treated) required to inhibit mold. Although calcium propionate is .used in the drawing, it will be understood that it is used as an example only and the effect of other salts, of salts of other acids and, in fact, the effect of our inhibitors generally, is similar in inhibition against mold. A large number of tests have shown that the variation in amount of 3-12 carbon atom acids and other salts than calcium propionate is not proportionately large, although as higher acids and acid salts are used it has been found that slightly smaller quantities of inhibitor are generally preferred to obtain the desired mold inhibition.

The inhibitor may be applied (as a solid, in case of a salt, or in solution) in any way appropriate to the material treated. If a surface is to be treated, as, for example, the surface of a foodstuff or other material susceptible to mold or the surface of a container or utensil used in the processing or handling of carbohydrates or other food materials or products, it may be sprayed with a solution of inhibitor of the proper concentration and pH value. If the inhibitor is to be incorporated in the processing of a food product such as bread, it may be added to the ingredients before, during, or after the mixing. For example, it may be added as a solution to the batch of bread dough or icing or in the case of a salt it may be mixed dry with or sprayed on flours, or meal or cereals. It may be admixed wtih or sprayed into sweet butter, pastries, custards or confections, cream cheese and cheese spreads. It may be applied to fruits, such as oranges, bananas, pineapples, grapes, apples, pears, by spraying or dipping.

Foods of the above type generally contain or are liable to absorb moisture or water and thus form good culture media for molds. A small quantity of inhibitor provides a salt or acid solution in such moisture suflicient to inhibit the formation of molds. When used to protect materials susceptible to mold, such as fruits, vegetables, tobacco, paper, leather, textiles, wood, belting or the like, or materials utilized in handling food products or other substances which are susceptible to mold, the inhibitors of this invention may be used in solution or, in the case of the salts, dry as desired. One of the advantages of the inhibitors of this invention is that by their use a somewhat greater quantity of water may be utilized, in bread making, thus adding greatly to the freshness and keeping qualities of the final loaf. This is of particular importance in the case of sliced bread.

A typical example is the following in which calcium propionate is incorporated in a bread batch, the bread described being typical of those.

white breads showing a pH of from about 5.1 to 6.0. Propionic acid was also utilized, in the same proportions and in the same manner. The results were as advantageous as in the use of calcium propionate of this example. In making the bread dough'a sponge containing 120 pounds of flour, 82 pounds of water, 3 pounds of yeast and 1 pound of yeast food was made and set at 78 F., to ferment for four and one-quarter hours. It was then made into a dough batch along with the following ingredients:

Pounds Flour 60 Water 33 Sugar 9 Powdered skim milk ,6 Shortening 5 /2 Salt 3% Malt extract 2 Calcium propionate To these ingredients, there is added, preferably, one ounce 'of ammonium bicarbonate. It will be understood that the ammonium bicarbonate, or other alkaline material, may be omitted without adverse effect upon the mold resistant qualities of the final bread product. However, as previously set forth, it is preferred to add this material because of the improvement in taste and general quality, of the finished bread.

The dough was mixed for 8 to 10 minutes at 80 F., and allowed to ferment of an hour before making into loaves. The calcium propiohate, above specified, was in the ratio of 56 pound to 115 pounds of water'and, therefore, somewhat over 0.4% and amply above that required for a pH value of 5.50 as shown in the accompanying drawing. While the calcium propionate may be valuable mineral nutritional constituent tothe product and hence is the preferred inhibitor of this invention.

In comparison with bread otherwise identical,

but containing no propionate, the bread above described was much more resistant to the growth of mold. When two loaves, one untreated and the other made as above, were inoculated with a mixture containing a variety of mold spores, then wrapped in paraflln paper and placed in an incubator at 96 F.. it was found that the untreated loaf contained a vigorous growth of mold after three days, while the bread treated with the propionate developed no visible growth of mold within six days.

When two loaves, both made in a bakeshop under identical normal conditions, one without propionate treatment and the other treated as above, were stored in an incubator, the untreated loaf showed mold growth in three days and was completely covered by mold in ten days, while the treated loaf containing calcium propionate did not develop any signs of mold growth after a period of about ten days.

As previously stated, however, the methods and inhibitors of this invention are applicable for prevention of mold growth in anything susceptible theretoi': Thus, for example, samples of cream cheese and a plurality of different cheese spreads and sweet butter were first heavily inoculated with mold, then treated withinhibitor by incorporation therein of 0.3% by weight calcium propionate, based upon the water content of the material treated, and finally placed in a closed vessel which was maintained at room temperature (summer). eras-30 C., and conditions of 50% and more humidity. At the expiration of a month under these accelerated conditions for mold growth no growth of mold could be seen, whereas samples run as controls but without inhibitor incorporation as above describedexhibited mold growth within 48 hours, the controls being under the same conditions of temperature and humidity as inhibited samples.

As an example illustrating the application of this invention by way of spraying the surfaces of the treated materials, similar samples of cream cheese, a number of different cheese spreads, and sweet butter were first heavily inoculated with mold and then the surfaces of the samples sprayed with a 2% water solution of calcium propionate and thereafter placed in a closed vessel and maintained therein at room temperature (around summer) of 25-30" 0., and conditions of 50%: and more humidity. The surfaces of the samples were sprayed sufficiently to insure that all the 1 perature and humidity above'described within hours.

In a manner similar to that previouslydescribed in connection with oh and butter, samples of tobacco were likewise treated by incorporation of approximately 0.3% by weight calcium propionate, based upon the water content of the tobacco, in the finely ground tobacco samples. These samples of tobacco were placed in a closed vessel along with controls,'both the inhibited sample and the control being heavily in: oculated with moldspores prior to placement in the closed vessel, and it was found that mold growth was inhibited in the treated ,sample for periods of over a month, where as the untreated materials exhibited extensive mold growth in 3 to 4 days. Similarly apples, pears, grapes, oranges and a number of other fruits and vegetables were treated by-a spray of a 2% calcium propionate solution, such as described in the treatment of cheese and tobacco, under the same accelerated conditions, and it was found that mold growth upon such fruits and vegetables was inhibited for a long period, whereas-controls which were not treated by the inhibitor exhibited mold growth within a very few days.

Mention has been specifically made above of the use of calcium propionate and propionic acid for incorporation in the material to be treated although other salts and other acids may similarly be utilized to accomplish the same purposes. Thus, for example, two samples of grape jelly, which is known to be extremely susceptible to mold growth, were treated by heavy inoculation of mold therein. One of the samples thereafter had incorporated in the jelly approximately 0.3%

sodium propionate, by weight, based upon the water content of the jelly, and the other sample, although heavily inoculated with mold, was not treated by incorporation of inhibitor therein. These two samples were placed in a closed vessel and maintained at room temperature (summer) of 25-30" C., and conditions of 50% and more humidity. At the expiration of about a month the inhibited sample showed no apparent mold growth, whereas the uninhibited sample showed extreme mold growth within 48 hours. Examples illustrating the use of the inhibitors of this invention could be multiplied extensively, but it is believed that the above cited examples are sumcient to show the scope of the present invention and its applicability to anything susceptible to mold.

Similarly, although concentrations of 0.3% by weight inhibitor have been described for incorporation, and 2-3% solutions of inhibitor for spraying, the concentrations in both. instances can be materially raised or lowered without detracting from the efficacy of the inhibitor, or resistance of the treated material to mold growth.

Various changes may be made in this invention without departing therefrom or sacrificing any of the advantages thereof.

We claim:

1. The method of inhibiting bread made from a fermented dough, other than sour dough bread made from non-glutenous flour, which comprises incorporating into the bread dough prior to baking mold inhibiting quantities of a material selected from the group consisting of propionic acid and its ammonium alkali metal and alkaline earth metal salts.

2. The method of inhibiting mold growth in bread made from a fermented dough, other than sour dough bread made from non-glutenous' mold growth in v flour, which comprises incorporating into the bread dough prior to baking a carbonate of ammonia and mold inhibiting quantities of a material selected from the group consisting of propionic acid and its ammonium, alkali metal and alkaline earth metal salts.

3. The method of inhibiting mold growth in bread made from a fermented dough, other than sour dough bread made from non-glutenous flour, which comprises incorporating into the bread dough'prior to baking mold inhibiting quantities of sodium propionate.

4. The method of inhibiting mold growth in bread made from a fermented dough, other than sour dough bread made from non-glutenous flour,

which comprises incorporating into the bread,

dough prior to baking mold inhibiting quantities of calcium propionate.

5. A method of making bread from a fermented dough other than sour dough bread made from non-glutenous flour, resistant to mold growth, which comprises incorporating in the bread dough a quantity of an agent of the class consisting of propionic acid and its ammonium, alkali metal and alkaline earth metal salts in an amount not exceeding about A;% of the weight of flour in said dough, and baking said bread.

6. A method of making bread from 'a fermented dough other than sour dough bread made from non-glutenous flour, resistant to mold growth, which comprises incorporating in the bread dough a quantity of an agent of the class consisting of propionic acid and its ammonium, alkali metal and alkaline earth metal salts in an amount not exceeding about of the weight of flour in said dough, fermenting said dough with yeast and baking.

'l. A method of inhibiting mold growth in bread made from a fermented dough other than sour dough bread made from non-glutenous flour, which comprises forming bread dough containing calcium propionate in quantity not exceeding about of the weight of flour in said dough, fermenting said dough with yeast and baking.

8. The method of inhibiting mold growth in bread made from a fermented dough other than sour dough bread made from non-glutenous flour, which comprises forming bread dough containing a small quantity of an ammonium carbonate, and containing calcium propionate in quantity not exceeding 'of the weight of flour of said dough, fermenting said dough with yeast and baking.

9. The method of inhibiting mold growth in bread made from a fermented dough, other than sour dough bread made from non-glutenous flour, which comprises incorporating into the bread dough prior to baking mold inhibiting quantities'of propionic acid.

10. The method of inhibiting mold growth in bread made from a fermented dough, other than sour dough bread made from non-glutenous flour, which comprises incorporating into the bread dough prior to baking a carbonate of ammonia and mold inhibiting quantities of calcium propionate. V

11. The methodof inhibiting mold growth in bread made from a fermented dough, other than sour dough bread made from non-glutenous flour, which comprises incorporating into the bread dough prior to baking a carbonate of ammonia and mold inhibiting quantities of propionic acid.

12. The method of inhibiting mold growth in bread made from a fermented dough, other than sour dough bread made from non-glutenous flour, which comprises incorporating into the bread dough prior to baking calcium propionate in quantity not exceeding about 0.5% of the weight of flour in said bread.

13. The method of inhibiting mold growth in bread made from a fermented dough, other than sour dough bread .made .from non-glutenous flour, which comprises incorporating intothe bread dough prior to baking ammonium bicarbonate, and calcium .propionate in quantity not exceeding about 0.5% of the weight of flour in said bread, the ammonium bicarbonate being equal to about A; to A; of the amount of propionate.

14. The method of making bread, other than sour dough bread made from non-glutenous flour, resistant to mold growth which comprises:

(1) making a sponge containing flour, water, 5 yeast and yeast food; (2) fermenting the resultant sponge; and, thereafter (3) incorporating said sponge in a bread dough together with a quantity of an agent of the class consisting of propionic acid and the alkali and alkaline earth metal propionates in amount not exceeding-about A of the weight of flour in the final complete method set forth in claim 10, and having the inhibitor uniformly distributed throughout the bread.

CHARLES HOFFMAN. GASTON DALBY. THOMAS R. SCHWEITZER. 

